1. Field of the Invention
The invention relates to an impeller of a blower, and more particularly, to an air-guiding impeller of a centrifugal blower having air-guiding ribs with a geometrical configuration for modulating the distribution of airflow.
2. Description of the Related Art
A centrifugal blower has a generally cylindrical impeller which is driven by a motor and the like disposed at the center thereof and which rotates in one direction so as to pull air in along its central axis as it rotates, and then forces the air radially outwardly, turning the air ninety degrees in effect. According to their air-intake path, the centrifugal blowers can further be divided into two categories: the single-suction blowers and the dual-suction blowers. A single-suction blower pulls air from only one side of the blower, while the dual-suction blower draws air in from both sides of the blower. Such centrifugal blowers are widely used in computers, copiers, printers, etc., to circulate the internal air for cooling.
A conventional centrifugal blower makes a lot of noise while performing the air circulation. For instance, a runner of a sirocco type fan has been disclosed in the Japanese Patent No. 126510 (hereinafter referred to as ""510 reference), as shown in FIGS. 1A and 1B. A main plate 2 made of a thick iron plate, which is fixed to a boss 3 of a rotary shaft 1 of the driving motor of the blower, transmits a rotary torque to the impeller comprising a plurality of blades 4. Each blade 4 is fixed at one end to one side of the main plate 2 at the outer periphery of the plate 2, and fixed at the other end to a side plate 5. The main plate 2 has several holes 6 to reduce the difference in the rigidity (or the distortion) of plates 2 and 5, and, in turn, reduce the stress produced in each blade 4. Since two ends of each blade 4 are fixed to plates 2 and 5 respectively, so the blade 4 can be placed in a severe environment, for example, the blades can sustain a high temperature blast. This is the primary object of ""510 reference. A thin sheet 7 is further fastened onto the other side of the main plate 2 so as to seal the holes 6 for blocking the air passage. FIG. 1C is a diagram showing the airflow path, illustrated by dotted lines, of a blower using the prior impeller structure shown in FIG. 1A. As the length of the blade 4 increases, the strength of the whole impeller decreases. So, it makes the fabricating processes more difficult. Moreover, in most cases, the intake air leaves the impeller before it can reach the lower end of blades 4, resulting in an empty area D in the airflow path and thus deteriorating the performance of impeller.
The ""510 reference also shows a second prior art shown in FIGS. 2A and 2B, wherein the rotary torque is transmitted to the impeller through a main plate 2 as in the above-described prior art. The main plate 2 is a thicker iron plate without any hole on it. An annular side plate 5 made of a thin iron plate is connected to the boss 3 of the rotary shaft 1 through several radial ribs 9 so as to reduce rigidity difference between plates 2 and 5, and stress produced in each blade 4. Each radial rib 9 is of a plane shape and is provided merely for connecting the plate 5 to the boss 3 and is integrally formed on the same plane with respect to the plate 5. However, the plane-shaped rib 9 is likely to disturb the inlet airflow of the blower, and thus deteriorate the fluid kinetics of the impeller.
Another embodiment of the ""510 reference is shown in FIG. 3. This embodiment is similar to the above-described embodiments except that two intermediate annular plates 12 and 13 are interposed between the main plate 2 and the side plate 5. Each of the intermediate annular plate 12 and 13 is provided with several holes, each of which fastens one of the blades 4 and prevents an intermediate portion of each blade 4 from becoming distorted. Each of the intermediate annular plate 12 and 13 is connected to the boss 3 of the rotary shaft 1 through several radial ribs 14. The radial ribs 14 are provided purely for connecting the intermediate annular plate 12 and 13 as described in the Japanese specification and are integrally formed on the same plane with respect to the intermediate annular plate 12 and 13.
Shown in FIG. 4 is another conventional impeller structure 31, which comprises a main plate 32 and a plurality of blades 34 integrally formed with the main plate 32 and evenly disposed along outer periphery on both sides of the main plate 32. Each upper blade 34 located on the top surface of main plate 32 aligns with a lower blade 34 in vertical direction. Therefore, these blades 34 of impeller 31 are xe2x80x9calignedxe2x80x9d , and the impeller 31 is called a xe2x80x9ccollateral impellerxe2x80x9d . Rotary torque from the rotary shaft 33 of the motor is transmitted to the blades 34 by the main plate 32. With this structure, the impeller 31 can be mounted into a dual-suction blower successfully. Compared to the blades 4 of FIG. 1A, the length of each blade 34 of FIG. 4 is only half of that of the blade 4, thereby increasing the strength of every blade and making the fabrication of the impeller easier.
Another impeller 41 is provided to reduce the noise, as shown in FIG. 5. It is known that the noise generated by a blower relates to the rotation speed and the dimension of its impeller. As the edge of blade passes through the tongue of the blower, it hums, which causes the noise. The impeller 41 is composed of a main plate 42, a plurality of upper blades 44 integrally formed with the main plate 42 and evenly disposed along the outer rim on the upper side of the main plate 42, and a plurality of lower blades 44xe2x80x2 disposed in a similar manner on the lower side of the main plate 42. The upper blades 44 and the lower blades 44xe2x80x2are alternately disposed. Rotary torque from the motor 43 is transmitted to the blades 44 and 44xe2x80x2 by the main plate 42. Comparing the impeller 41 with the impeller 31 shown in FIG. 4, the length of a blade edge passing through the tongue of the blower per unit time is reduced by half, while the frequency of the hum increases. As a result, the noise generated by the impeller 41 can be reduced effectively by carrying a lower amplitude.
FIGS. 6A-6C are diagrams showing the airflow path of an impeller having a structure as shown in FIGS. 4 or 5. Referring to FIG. 6A, the main plate 42 has no hole for airflow. The impeller 41 works well in a dual-suction blower when the air-intake path on both sides of blower is fluent. However, when a blower is mounted closely on a surface W, as shown in FIG. 6B, the airflow path from the lower side of the blower is blocked. As a result, the performance of the impeller deteriorates. In addition, when the impeller 41 is mounted onto a single-suction blower, as shown in FIG. 6C, the main plate 42 blocks the supply of airflow from the upper side. Thus, the intake airflow can only be applied to the upper blades. Thus, the impeller 41 becomes even less inefficient when mounted onto a single-suction blower.
It is an object of the invention to provide an impeller of a blower having air-guiding ribs with a geometrical configuration and formed on a different plane with respect to an annular frame, thereby modulating the distribution of airflow more evenly, reducing the noise generated during the operations of the blower, and increasing the air suction force and the intake airflow.
It is still an object of the invention to provide an impeller of a blower having air-guiding ribs with a geometrical configuration which is adaptable for either a dual-suction blower or a single-suction blower.
It is yet still another object of the invention to provide an impeller of a blower which can eliminate an empty area of the intake airflow formed within the impeller by providing air-guiding ribs with a geometrical configuration and formed on a different plane with respect to an annular frame.
Accordingly, the impeller of the invention includes a rotary shaft adaptable for a motor, an annular frame, a plurality of blades formed on the annular frame, and a plurality of air-guiding ribs each interconnected between the annular frame and the rotary shaft inclined with respect to the annular frame. Each of the air-guiding ribs is characterized by forming on a different plane with respect to an associated annular frame and having a geometrical configuration selected from the group consisting of an eye shaped profile, a tear drop shaped profile, a parallelogram profile, a triangular profile, a slide shaped profile, a wave shaped profile, a rod shaped profile and a rhombus profile. As the air-guiding impeller rotates, the air is first pulled inwardly from the outside of the blower and then forced radially outwardly by the blades. During the same time, the air-guiding ribs with a featured cross-sectional profile induce an increased partial intake airflow into the blower, thereby modulating the distribution of the airflow within the blower and increasing the suction force and the intake airflow. Moreover, the present invention can reduce the noise because the length of blade edge passing through the tongue of blower per unit time is reduced by half.